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在我国发育稠油的含油气盆地中,广泛分布着浅层天然气,浅层气资源潜力巨大.研究发现这些浅层天然气与稠油具有密切的成因关系,是厌氧微生物降解原油过程中形成的次生成因的生物气,也称为稠油降解气,它们一般分布在稠油油藏的上倾方向或周围.这种天然气以干气为主,主要成分是甲烷,乙烷以上的重烃类含量较低,非烃中N2含量较高;甲烷的碳同位素值偏轻,一般介于生物气与热解气之间,乙烷的碳同位素偏重,可能混合有热成因气;CO2显示出异常重的碳同位素值,因此,在微生物降解原油过程中碳同位素分馏效应十分明显.稠油降解气的生成是一个十分复杂的地质地球化学和微生物地球化学过程,是在多种微生物群体参与下发生的一系列有机-生物和水-烃反应综合作用的结果,受多种因素控制.
The shallow natural gas is widely distributed in the petroliferous basins with heavy oil in our country and the potential of shallow gas resources is huge.It is found that these shallow gas have a close genetic relationship with heavy oil and are formed during the degradation of crude oil by anaerobic microorganisms Biogas secondary to formation, also known as heavy oil degradation gas, is generally distributed in or around the updip of heavy oil reservoirs, mainly dry gas, with major components being methane, heavier hydrocarbons above ethane The carbon content of methane is relatively low, generally between biogas and pyrolysis gas, and the carbon isotope of ethane is biased, and may be mixed with pyrogenic gas. CO2 shows Therefore, the carbon isotope fractionation effect is very obvious during the microbial degradation of crude oil.The formation of heavy oil degraded gas is a very complex geological geochemical and microbial geochemical process, is involved in a variety of microbial populations The result of a combination of organic-biological and water-hydrocarbon reactions takes place under a number of factors.